Incandescent light bulbs create light by conducting electricity through a resistive filament and heating the filament to a very high temperature to produce visible light. Incandescent bulbs are made in a wide range of sizes and voltages. The bulbs typically include an enclosure with a tungsten filament inside and a base connector that provides both an electrical and structural support connection. Incandescent bulbs generally mate with a lamp socket having a threaded Edison base connector, bayonet base connector, pin base connector, or any suitable connector for providing electrical power to the bulb. However, incandescent light bulbs are generally inefficient and require frequent replacement. These lamps are in the process of being replaced by more efficient types of electric light such as fluorescent lamps, high-intensity discharge lamps, and, in particular, LED light sources.
LED technology continues to advance resulting in improved efficiencies and lower costs with LED light sources found in lighting applications ranging from small pin point sources to stadium lights. An LED light may be 60-70% more efficient than an incandescent light but may still generate significant amounts of heat. At higher temperatures, light conversion efficiency for an LED light source may drop as power increases, the LED life decreases, and the light output from the LED may be permanently diminished.
An LED light source is generally chip mounted and heat is conducted away through a heat sink. Existing light fixtures are largely adapted to dissipate radiated heat and usually have very little capacity to dissipate conducted heat. In order to reach desired lumen values and maintain compatibility with a significantly large installed base of presently existing fixtures, additional cooling techniques may be required. It would be advantageous to provide an LED lamp that closely resembles an incandescent lamp in light output and aesthetics, with the high efficacy and life of an LED light source.
A variety of LED lamps with full glass outer jackets in A-line and candelabra embodiments have been introduced. While these products preserve the incandescent aesthetic, they are often not dimmable. LED lamps that are dimmable typically have poor dimmability (e.g. small dimmable range of only 100% to ˜50%, and/or noisy operation while dimmed) and/or low power factor (e.g. 0.4-0.6).
Additionally, in some cases LED lamp products do not meet UL (Underwriters Laboratories) standards because the LEDs do not self-extinguish if the glass bulb is broken. LED lamps that are receiving UL approval have the glass bulb coated with silicone so the glass is shatter resistant.
Accordingly, it would be desirable to provide LED lamps that solve at least some of the problems identified above.